Process for refining copper and its alloys



Patented Nov. 2, 1948 PROCESS FOR REFINING COPPER AND v ITS ALLOYS Michael George Corson, New York,

N. Y., assignor to The Linde Air Products Company, a corporation of Ohio N Drawing. Application June 15, 1946, Serial No. 677,102

4 Claims.

The present invention relates to an improved process of producing sand castings from copper and copper alloys, and more particularly to the production of sand castings of such, metals that are characterized by soundness and high values of the physical characteristics, notably electrical and heat conductivities.

Ordinary copper resulting from the remelting of cathode copper is pure enough to produce castings of high conductivity. However, during the process of melting the metal absorbs oxygen and hydrogen as well as sulphur dioxide from the fuel and if cast directly produces extremely porous castings whose tensile strength hardly reaches 16,000 lbs. per square inch or 50% of the strength of Wrought and annealed copper. Besides, the oxide of copper comprised in the eutectic around the grains of copper is likely to become reduced and cause the casting to develop brittleness.

The oxides canbe removed by the addition of a numb r of elements but any excess of the latter will either go into solid solution and lower the conductivity or stay in the eutectic andlower the ductility. Furthermore. a deoxidationfldoes not mean deeasification. The casting may contain no oxide of copper and still be highly porous.

One of the most successful methods of preparing sand castings from copper that has heretofore been practised consists in a judicious addition of a copper-calcium-silicon alloy to molten copper brought to 2400-2500 F. or about 400500 F. above its melting point. The oxides are removed and the small amount of silicate flux that is formed serves to prevent further oxidation while the metal and its container are cooled down to around 2100 F. before pouring. During this period of cooling a large amount of gases escape and good castings result. But their conductivity varies and cannot be guaranteed to go above 85% of standard pure copper. The tensile strength cannot be guaranteed to be above 22,000 lbs. per sq. inch.

In order to improve the molten metal by a far reaching deoxidation and degasification I have developed the following method:

Copper is melted by any of the usual methods. It may be covered by a flux, if desired, but ordinarily this is not needed. The melt is then superheated. A temperature within the range 2200- 2400 F. is usually ample. By way of example, the temperature is brought to 2300 F. or thereabouts and a preheated pipe of graphite or a tubing of fused silica is then introduced into the metal while the container is still in the furnace. The pipe will be introduced almost to the permitted to drop bottom of the container so as to insure that gas introduced therethrough will first come into contact with the melt in the lower portions thereof and, in passing upward to the surface, will become thoroughly mingled with the metal in the upper portions of the melt. If a single pipe is used, it should, of course, be moved about in the bath to insure that gas will be introduced more or less uniformly. Thispipe or tubing is connected by a hose or suitable piping and two valves to two containers of gas. One container carries carbon monoxide and the other nitrogen. Carbon monoxide is blown in first and for a 300 lb. melt contained in a crucibleor ladle, usually with in one minute it will bring about a complete 'deoxidation of the metal. Next the valve connecte ing the pipe with the nitrogen container is opened and the one leading to the carbon monoxide container is closed. When treating a melt in a crucible or ladle of 300 lbs. capacity all hydrogen, sulphur dioxide and the dissolved carbon monoxide usually will be blown out in three minutes. The metal then can be taken out of the furnace and poured into the molds. When cold the castings produced in this manner will have a. density of 8.92 against the maximum of 8.94 for perfectly pure copper. Their conductivity is above 96% and may even equal 98% of standard copper. The ultimate tensile strength runs about 2800-3000 lbs. per sq. inch and the ultimate elongation about The method was developed primarily for the production of high conductivity copper castings but can be used for the degasification of any copper alloy and in the case of such alloys that contain either aluminum, silicon or tin it helps to remove the solid oxides present in the form of fifms. In the case of alloys containing in addition to copper only nickel, zinc or antimony or any combination of these metals, the treatment will also reduce any oxides of the ,metals that are present.

Once the deoxidation and degasification have been completed, the metal may be poured at any suitable temperature. In fact, the temperature of the melt may be permitted to fall during the course of the degasification treatment to the final pouring temperature, say to close to 2100 F. when copper is being treated. However, for copper the temperature preferably should not be below the indicated range of 2200-2400" F. until after the deoxidation step is completed.

Although the invention has been described with particular reefrence to the production of sand applying the above described treatment to the metal before casting.

It will be understood that various changes may be made in the details of the procedure within the skill of the workers in the art without departing from the invention. The invention is not to be deemed as limited otherwise than as indicated by the language of the appended claims.

I claim:

1. The process of treating copper and copper alloys to improve their soundness and other phys ical characteristics when used as sand castings and the like which comprises forming a melt of the metal to be cast, superheating the melt and, while the melt is maintained in a superheated state, successively blowing carbon monoxide and nitrogen into and through the melt, the duration of the treatment with carbon monoxide being suificient to insure substantially complete deoxida tion of the metal and the nitrogen treatment being continued until substantially all hydrogen, sulphur dioxide and dissolved carbon monoxide are removed from the melt.

2. The process of treating copper and copper alloys to improve their soundness and other physical characteristics when used as sand castings and the like which comprises forming a melt of the metal to be cast and while the melt is maintained at a temperature in the neighborhood of 2300 F., successively blowing carbon monoxide and nitrogen into and through the melt, the duration of the treatment with carbon monoxide being sufiicient to insure substantially complete cleoxidation of the metaland the nitrogen treatment being continued until substantially all hydrogen, sulphur dioxide and dissolved carbon monoxide are removed from the melt.

3. The process of treating copper and copper alloys to improve their soundness and'other physical characteristics when used as sand castings and the like which comprises forming a melt of the metal to be cast, superheating the melt and,

while the melt is maintained in a superheated state, successively introducin carbon monoxide and nitrogen into the melt in the portions thereof adjacent the bottom of the vessel containing the same and permitting the introduced gas to pass upward through the melt to the surface thereof, the duration of the treatment with carbon monoxide being suflicient to insure substantially complete deoxidation of the metal and the nitrogen treatment being continued until substantially all hydrogen, sulphur dioxide and dissolved carbon monoxide are removed from. the melt.

4. The process of treating copper to improve its soundness and electrical conductivity when used as sand castings and the like which comprises forming a melt of the copper to be cast while the melt is maintained at a temperature in the range of 2200 F. to 2400 F., successively blowing carbon monoxide and nitrogen into and through the melt, the duration of the treatment with carbon monoxide being sufiicient to 111-- sure substantially complete deoxidation of the metal and the nitrogen treatment being continued until substantially all hydrogen, sulphur dioxide and dissolved carbon monoxide are removed from the melt.

MICHAEL GEORGE CORSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

